Comparative Study on Cumulative Effect of Short-Circuit in Single-Phase and Three-Phase Transformers

Abstract

The transformer windings will suffer cumulative damage under the influence of multiple short-circuit loads. Once the load exceeds the limit that the structure can withstand, a permanent damage accident will occur. Therefore, it is of great significance to study the cumulative effect of short-circuit of transformer. Few studies have discussed the cumulative effect of single-phase and three-phase transformers and their differences. In this work, based on the deformation mechanism of transformer windings, a finite element model of transformer is established, and the distribution of magnetic field and electromagnetic force of windings during short-circuit are obtained. Then, the cumulative effects of single-phase and three-phase transformers are compared under multiple short-circuit impacts. The results show that when the single-phase transformer is subjected to multiple short-circuit im-pacts, the internal residual stress and deformation of windings continue to accumulate. Due to the influence of the short-circuit current of adjacent phases in a three-phase transformer, the stress, displacement, and plastic strain of one-phase winding increase with the short-circuit current of the other phases. It is easier to reach the tolerance limit of windings than the single-phase transformer. This research will provide a reference for evaluating the short-circuit withstand capability of power transformers.